Eisuke Kudoh

Study on construction of wireless transmission simulator by H8 microcomputer board

Various techniques have been studied in order to realize high-speed wireless network. Many wireless transmission technologies are usually validated by theoretical analysis or computer simulations assuming ideal conditions. However, actual wireless transmission performance may be degraded by the error caused by hardware limitation. Therefore, it is necessary to validate these techniques by hardware simulations for practical use. Furthermore, the visualization of the waveform by an oscilloscope or a spectrum analyzer is helpful for promotion of research. Cognitive radio system which can change the modulation scheme, i.e. adaptively by rewriting the software, has attracted attention. There is a great demand for general purpose software defined wireless transmitter and receiver. Such wireless transmitter and receiver can be realized using signal generator and vector signal analyzer which are commercial products. However, these equipments are most of the time expensive. There exist also inexpensive devices like H8 microcomputer board. This can be programmed using C language. However, because of the limitation of H8 microcomputer board hardware performance, high-end functions are not available and the size of variable is limited. Under such constraints, by using a single H8 board microcomputer, inexpensive wireless transmission simulator is constructed in this paper. We build a simulator of an OFDM transmitter, an OFDM receiver, a frequency selective fading simulator, and a noise generator. The signals are visualized by an oscilloscope. The bit error rate performance is evaluated and the results well agree with the theoretical values.

Location estimation method using side information

In indoor environment, it is difficult to receive directly radio waves from satellites, and thus accurate location estimation is difficult using satellites signals. Since mobile communication propagation channel suffers from fading and shadowing, it is difficult to estimate accurate location in indoor environment only using the received signal power. In addition to using received signal power, we propose the use of side information for location estimation by multiple regression analysis. Our proposed method is validated by experiment and compared with the conventional method which only uses the received signal power. It is found that the proposed location estimation method can reduce the estimation error compared with the conventional estimation one.

Study of an Iterative Resource Allocation Algorithm for a 2-Hop OFDMA Virtual Cellular Network

Multi-hop networks can increase the data transmission rate in the next generation mobile network. A new resource allocation algorithm is required for this new type of network architecture. A multi-user resource allocation scheme has been proposed for a 2-hop OFDMA virtual cellular network (VCN). Using that scheme, the VCN can provide better channel capacity than the single hop network (SHN) for low transmission power. However, in the interference dominant transmission power region, the SHN performs better than the VCN. This paper proposes some iterative schemes to increase the channel capacity of the VCN. Using computer simulations, this paper shows that applying those iterative schemes can augment the ergodic channel capacity of the VCN in the interference dominant transmission power region.

Study of the Degree of Fairness for a Parallel Relay 2-Hop OFDMA Virtual Cellular Network

With the trend of the evolution of Information and Communication Technology (ICT), high data rate transmission is expected and needed in the next generation mobile network. In order to maintain the same quality of service, the transmission power would need to be increased if the current mobile cellular network architecture is to be considered. To solve this problem, a multi-hop virtual cellular network (VCN) has been proposed. The simulation results of a resource allocation algorithm with interference for a parallel relay 2-hop OFDMA virtual cellular network have shown that the VCN can achieve a better channel capacity than the single hop network for low transmission power. In this paper, using this algorithm, we evaluate the channel capacity of the VCN as the number of users increases, and study the degree of fairness of the VCN compared with that of the conventional single hop network. For low transmission power, the simulation results show: a) the channel capacity of the VCN remains better than that of the single hop network as the number of users increases, and b) the VCN can achieve a better degree of fairness than the single hop network.

MMSE location estimation using multiple items of sensed information in indoor environments

Receiving radio waves directly from satellites is difficult in an indoor environment, making accurate location estimation by satellite signals difficult. Since mobile communication propagation channels suffer from fading and shadowing, estimating accurate locations in an indoor environment by using only the received signal power of a radio wave is also difficult. In addition to using the received signal power, we have proposed the use of multiple items of sensed information for location estimation by multiple regression analysis, and we have shown that this method can reduce estimation errors compared with the conventional one. However, information with the exception of the received signal power does not necessarily change linearly with distance. In this paper, we propose a minimum mean square error (MMSE) location estimation method. This method estimates the location that minimizes the mean square error between multiple items of sensed information and a constructed database that provides the relationship between the location and the multiple items of information. Our method is experimentally validated and compared with the conventional linear regression method. Our method was found to reduce the standard deviation of the location estimation error to less than 1/4, and the probability that the estimated distance is equal to the actual distance is about three times as high compared with the linear regression method.

Study on construction of CDMA transmission simulator using SH3 microcomputer board

A lot of techniques have been studied in order to realize high-speed wireless networks. Many wireless transmission techniques are usually validated by theoretical analysis or computer simulations assuming ideal conditions. However, actual wireless transmission performance may be degraded by errors caused by hardware limitations. Therefore, validating these techniques by hardware simulations for practical use is necessary. Furthermore, the visualization of a waveform by an oscilloscope or a spectrum analyzer is helpful for promoting research. Cognitive radio systems that can adaptively change the modulation scheme by rewriting software have attracted attention. There is a great demand for general purpose, software defined wireless transmitters and receivers. We have constructed a wireless transmission simulator by using a single inexpensive H8 microcomputer board. However, transmitting 100,000 bits takes about 60 hours, making it difficult to verify transmission performance under 10-3. We also have an SH3 microcomputer that has higher processing performance than an H8 microcomputer. In this paper, we describe the construction of a CDMA wireless transmission simulator using an SH3 microcomputer board. The signal waveform has been visualized by oscilloscope, and the BER performance has been evaluated. The transmission rate when using the SH3 microcomputer board has been shown to be 140 times or higher than that when using the H8 microcomputer board.

Study on construction of wireless 2-hop transmission simulator by H8 microcomputer board

Various techniques have been studied in order to realize high-speed wireless network. Many wireless transmission technologies are usually validated by theoretical analysis or computer simulations assuming ideal conditions. However, actual wireless transmission performance may be degraded by the error caused by hardware limitation. Therefore, it is necessary to validate these techniques by hardware simulations for practical use. Furthermore, the visualization of the waveform by an oscilloscope or a spectrum analyzer is helpful for promotion of research. Cognitive radio system which can change the modulation scheme, i.e. adaptively by rewriting the software, has attracted attention. There is a great demand for general purpose software defined wireless transmitter and receiver. Such wireless transmitter and receiver can be realized using signal generator and vector signal analyzer which are commercial products. However, these equipments are most of the time expensive. There exist also inexpensive devices like H8 microcomputer board. This can be programmed using C language. However, because of the limitation of H8 microcomputer board hardware performance, high-end functions are not available and the size of variable is limited. In this paper, we build a 2-hop wireless transmission simulator by using a single H8 board microcomputer. The signals are visualized by an oscilloscope. The bit error rate performance is evaluated and the results well agree with the theoretical values.

On the channel capacity of multi-hop virtual cellular network

In the next generation mobile communication systems, high speed data services are expected. However, an unacceptably high transmit power is required. Multi-hop technique can solve this problem. To reduce the transmit power, while increasing the transmission data rate, we have proposed a wireless multi-hop virtual cellular network (VCN). In this paper, we introduce the multi-hop VCN for high speed wireless network and discuss the channel capacity performance of the multi-hop VCN.